1. Field of the Invention
The invention relates to apparatus and methods for continuous high speed wrapping of labels onto upright containers.
2. Prior Art
Mechanical handling of containers for label application normally includes a number of components integrated to operate as a unit for wrapping a label onto a container. Such apparatus, as disclosed in U.S. Pat. No. 4,242,167, may include a means of label stock supply, a means for cutting label segments, an adhesive assembly for applying adhesive or glue to label segments, a vacuum drum for transfer of the label segments to a position where they are wrapped onto a container, and means for feeding containers to and away from the labeling position. Speed limitations of any one subcomponent have been found to limit the speed of the overall operation. The apparatus of U.S. Pat. No. 4,242,167 is designed to operate at a speed of approximately 100 containers per minute.
It has been discovered that adhesive application methods used in prior apparatus do not accommodate a high speed labeling operation. A glue roller/glue bar assembly is commonly used for imprinting a glue pattern onto labels. As disclosed in U.S. Pat. No. 4,104,845, hot melt adhesive is channeled from a reservoir through a passageway inside a glue "bar". The passageway terminates in a glue deposit portal on the surface of the glue bar, in face-to-face contact with the roller. Glue deposited onto the roller surface becomes increasingly difficult to spread and drain. Excess blue results in uneven, messy printing. In addition, when the apparatus is operated at a speed exceeding 600 containers per minute, the glue may fling off the roller.
Another significant disadvantage of the prior art is that the overall speed of a labeling operation is limited by the discharge conveyor. The rate of discharge must be adjusted to accommodate spinning and instability of exiting containers. As shown in U.S. Pat. Nos. 3,765,991 and 3,834,963 conventional apparatus discharges containers between a single belt positioned opposite a stationary wall. This design, however, imparts additional instability to exiting containers and does not permit container discharge in excess of 600 containers per minute.
It is the object of this invention to achieve high speed labeling of containers by overcoming the disadvantages of the prior art.
It is another object of this invention to avoid such disadvantages by providing an apparatus and method which places labels on containers at high speeds while efficiently spreading and draining glue.
Another object of this invention is to enable a high speed labeling operation by stabilizing exiting containers in order to operate the discharge conveyor at high speeds.
It is a further object of this invention to prevent instability during discharge in order to enable operation at speeds of 1000 or more containers per minute.